Current systems used for configuration of digital modules of various electrical systems, such as those used in the operation and control of medical equipment, are configured for a specific type of configuration with normal jumpers. For example, a carrousel controller for a clinical linear accelerator system has a general configuration on the auxiliary electronic backplane of the system that generates configuration frequencies for the control system. The controller for the carrousel usually has a specific set of software instructions, generally through a PROM, and a configuration specific set of phase analysis lines (PALs). In operation a CPU is used to compare the configuration frequencies from the backplane, the PAL signals, and the family of signal types allowed by the software; the CPU then ensures that all three components match before normal operation of the digital control system is allowed. Proper signal type identification is ensured by the configuration specific frequencies, since these frequencies will not be subject to "stuck-at-X" faults as would occur when a poor pin connection in the normal jumpers existed. Checks against poor jumper connections are prevented by verifying the configuration frequencies against the PAL configuration specific signal type codes. These systems are considered fault-tolerant; however they are prone to failure due to radiation and other common electronic device failure modes.
The present systems, however, still are subject to erroneous fault indications as a result of a dysfunctional jumper or faulty pin. This fault tolerant system is not acceptable in critical environments, such as medical device control systems, where all possible failure modes must be checked as a normal part of circuit operation to guarantee fault-free output.